Recent work has highlighted the strong relationships among obesity, diabetes, and the metabolic syndrome as causes of low urinary pH. Low urinary pH in turn is the major urinary risk factor for uric acid stones. Unlike calcium stones, uric acid stones can be dissolved and easily prevented with adequate urinary alkalinization. Recognizing the relevant risk factors should lead to increased identification of these radiolucent stones. The cornerstone of therapy is raising urinary pH; xanthine dehydrogenase inhibitors should be used only when urinary alkalinization cannot be achieved.

Department of Medicine, New York University Langone Medical Center, New York, NY; and Nephrology Section, New York Harbor VA Healthcare System, and Endourology Section, Lenox Hill Hospital and Division of Nephrology, New York University Langone Medical Center, New York, NY.